1. Field of the Invention
The present invention relates t,o a semiconductor memory. More particularly, the present invention relates to the circuits that control the supply of power to the sense amplifiers in a semiconductor memory.
2. Description of the Related Art
Sense amplifiers have the job of amplifying small potential differences between pairs of bit lines. In a conventional memory the sense amplifiers are powered from a pair of supply lines that are coupled to a power supply node and a ground node through respective transistors. When these transistors are switched off, the supply lines are precharged to one-half the power-supply potential. When the transistors are switched on, the supply-line potentials diverge toward the power-supply potential and ground. The sense amplifiers are adapted so that the potentials of each pair of bit lines likewise diverge, the bit line that was originally higher being pulled lip to the power-supply potential while the bit line that was originally lower is pulled down toward ground.
A problem with the conventional scheme is that it provides no assurance that the two supply-line potentials will diverge uniformly. In particular, any timing difference between the signals that control the above two transistors is translated directly into a timing difference between the waveforms on the supply lines, as a result of which the pull-up and pull-down circuits the sense amplifiers fail t,o operate with coordinated timing.